5. TREATMENT OF POULTRY SLAUGHTERHOUSE WASTEWATER USING A
5.3 Material and methods
5.3.1 Experimental set-up and equipment
Figure 5.1 represents the laboratory bench-scale SGBR anaerobic digester coupled with the UF membrane system that was operated for 64 days. The purpose of the bench-scale SGBR reactor was to reduce the organic load of the feed after the effluent passed through the UF membrane systems. The bench-scale SGBR anaerobic digester consisted of a polyvinyl chloride (PVC) cylinder-shaped reactor with a total working volume of 1.53 L and an inner diameter and height of 0.071 m and 0.5867 m, respectively.
60 Figure 5.1: Schematic diagram for the laboratory bench-scale SGBR coupled with ultra -filtration (UF) membrane system
Separate 5 L polypropylene sample containers were used to store wastewater prior to and after treatment. A perforated PVC pipe was placed at the top of the SGBR to distribute the feed across the entire cross-section of the reactor. Pea gravel with an average diameter of 5 mm was used as an under-drain to prevent granular sludge washout and clogging of under-drain pipes. A 2-mm grit sieve was positioned at the bottom of the SGBR to retain the pea gravel. Silicone tubing was used for an overflow line and a backwash system was installed for declogging. The influent was fed at the top of the reactor using a multi head Gilson (Germany) peristaltic pump and the effluent was simultaneously withdrawn from the bottom of the SGBR at the same rate. The reactor operated at a mesophilic temperature ranging between 35 and 37°C. The water jacket temperature was regulated and circulated using a thermostatic water bath. The reactor was also insulated to prevent heat losses to the environment. The biogas produced was collected in a 0.50 L plastic Tedlar bag through an outlet port installed at the top of the SGBR. The SGBR reactor was backwashed using the SGBR effluent using the backwash line to remove suspended solids accumulating on the pea gravel to prevent the system from clogging.
5.3.2 Slaughterhouse wastewater
The poultry wastewater was collected from a slaughterhouse located in the Western Cape, SA. The characteristics of the wastewater are summarized in Table 5.2 which lists average values of parameters quantified over a 9-week sampling period. All measurements were performed according to standard methods (APHA, 2005).
62 Table 5.2: Characteristics of the wastewater from a poultry slaughterhouse in the Western Cape, South Africa (quantified, as no published data available in SA)
Parameter Unit Poultry slaughterhouse waste water
Range Average
pH 6.5-8.0 -
Alkalinity mg/L 0- 489 489
Total chemical oxygen
demand mg/L 2133-4137 2903
Soluble chemical
oxygen demand mg/L 595-1526 972
Biological oxygen
demand mg/L 1100-2750 1667
TKN mg/L 77-352 211
Ammonia mg/L 29-51 40
TKN mg/L 77-352 211
Total Phosphorus mg/L 8 – 27 17
Fats, oil and grease mg/L 131-684 406
Total dissolved
oxygen mg/L 372-936 654
Total suspended
solids mg/L 315-1273 794
Volatile suspended
solids mg/L 275-1200 738
Soluble proteins mg/L 0-368 72
Volatile fatty acids mg/L 96-235 235
5.3.3 SGBR inoculation and start-up procedure
The SGBR was inoculated with 0.95 L of anaerobic granular sludge collected from a full-scale up-flow anaerobic sludge bed (UASB) reactor operated at a local brewery (Newlands Brewery, Western Cape, SA). Poultry slaughterhouse wastewater (collected from a slaughterhouse in the Western Cape, SA), with a volume of 0.43L, was also added to the SGBR to initiate the process. A Gilson peristaltic pump was fed the wastewater into the SGBR. Dry milk solution prepared with distilled water, with a tCOD concentration of 2000 mg/L, was used as feed during the acclimation period of 48 hr.
5.3.4 SGBR operating conditions
Collected poultry slaughterhouse wastewater samples were refrigerated at a temperature of 4˚C. The poultry slaughterhouse wastewater was diluted with distilled water to prevent shock loading during the acclimatization period. During the last 36 days of the SGBR operation, the bioreactor was fed with the undiluted poultry slaughterhouse wastewater. After the acclimation period of 48 hr, the flow rate was adjusted to 27.8 mL/h (HRT to 55 h) with the system then allowed to reach steady state. The HRT of 55 h was maintained for a total of 44 days with an average OLR of 1.01 g COD/L.day. To start the process, the SGBR was fed with 50% of the diluted poultry slaughterhouse wastewater for the initial 19 days (1:1 ratio), followed by diluted poultry slaughterhouse wastewater with a concentration of 67% (2:1 ratio) for the subsequent 9 days. Thereafter, undiluted poultry slaughterhouse wastewater was fed to the SGBR for an additional 16 days while maintaining an HRT of 55 h.
The HRT was further reduced to 40 h during the last 21 days of operation by increasing the feed flow rate to 38.3 mL/h. The average OLR of the undiluted feed used during this period was 3.14 g COD/L.day. Table 5 provides the operating conditions governing the continuous operation of the SGBR over a period of 64 days.
The treated wastewater generated by the SGBR was used as the feed for the bench- scale UF membrane post-treatment system.
Table 5.3: Operating conditions (HRT and OLR) for the SGBR system over a period of 64 days
Dilution (% )
Operating Time (days)
Flow rate (mL/h)
HRT (hrs)
OLR (g COD/L.day)
50 67 None None
1-19 20-28 29-44 45-64
27.8 27.8 27.8 38.3
55 55 55 40
0.56 0.67 1.73 3.14
5.3.5 The ultra-filtration (UF) membrane system
An inorganic membrane with an inner diameter of 2 mm and an outer diameter of 3 mm was utilised as a post-treatment system for the SGBR reactor. The membrane consisted of alpha aluminium oxide (Al203) ceramic material with a membrane pore size of 40 nm. The UF membranes were operated under a dead-end flow
64
reduction. The clogged UF membranes were then back-washed to remove suspended solids with the membrane surface appearing free from the gel-layer deposit.
5.3.6 Analyses of poultry slaughterhouse wastewater
The performance of the SGBR was monitored using untreated and treated wastewater, focusing on analyses of the following: pH, temperature, conductivity, TDS, salinity, turbidity, TSS and tCOD. Samples of the SGBR feed and product streams including UF permeate were taken every second day (i.e. Mondays, Wednesdays and Fridays) for in-house analyses in duplicate. A weekly sample of the SGBR product and UF permeate was taken to an external South African National Accreditation System (SANAS) accredited laboratory (Scientific Services, City of Cape Town, South Africa) for tCOD, FOG, TSS, VFA and alkalinity analyses.